The present invention pertains to a technical field of a seat belt device of which a seat belt for restraining and protecting an occupant sitting on a vehicle seat is connected to a vehicle body on a side of the vehicle seat and, particularly, to a technical field of a seat belt device for a vehicle seat which is provided at its lower portion with a seat weight sensor for measuring a seat load applied to the vehicle seat.
Conventionally, a seat belt device installed in a vehicle such as an automobile prevents an occupant from jumping out of a vehicle seat by restraining the occupant with a seat belt thereof, thereby protecting the occupant in the event of emergency.
As such seat belt device, three-point-type seat belt devices which are conventionally well known are generally employed. In a three-point-type seat belt device, one end of a seat belt is connected to a vehicle body or a vehicle seat fixed to the vehicle body on a side of the vehicle seat via a lap anchor fixed to the seat belt, while the other end of the seat belt is connected to a seat belt retractor. In this case, a middle portion of the seat belt is guided by a deflective fitting attached to an upper portion of a side of the vehicle body.
When the seat belt is not worn, the seat belt is wound by the seat belt retractor and is positioned to extend along the side of the vehicle body. By latching a tongue slidably supported by the seat belt with a buckle fixed to the vehicle body on the opposite side of the lap anchor side about the vehicle seat, an occupant sitting in the vehicle seat puts on the seat belt. In this state, a portion of the seat belt between the tongue and the deflective fitting (seat belt retractor side) functions as a shoulder belt for restraining and protecting an upper body of the occupant from his or her shoulder to his or her chest, while a portion of the seat belt between the tongue and the lap anchor functions as a lap belt for restraining and protecting a lower body of the occupant such as his or her abdomen.
On the other hand, in recent years, it has been developed to control the action of the seat belt device depending on the weight (body weight) of the occupant. In such seat belt device, a seat weight sensor for measuring the seat load, applied to the vehicle seat by the weight of the occupant and the like, is installed below the vehicle seat and between the vehicle seat and a vehicle body floor. By controlling the action of the seat belt device depending on the weight of the occupant based on the seat load measured by the seat weight sensor, the occupant can be effectively restrained by the seat belt, as described in Japanese Patent Unexamined Publication No. H11-304579, and Japanese Patent Unexamined Publication No. H11-351952 (both incorporated by reference).
In the seat belt device for the vehicle seat which is provided at its lower portion with the seat weight sensor, the lap anchor for connecting one end of the seat belt to a vehicle body is positioned on a side of the seat weight sensor. However, since convex structural components of the vehicle body such as a pillar and a side sill depending on the vehicle structure exist on the side of the seat weight sensor, the space on the side of the seat weight sensor must be significantly narrow. Therefore, it is a bother and thus difficult to connect the lap anchor fixed to the end of the seat belt to the vehicle body floor or the vehicle seat or the seat weight sensor fixed to the vehicle body so that the work for this must require a lot of labor and time.